1 of 25
Background to the PFRA European Overview - UC9810.5b
The individual Member State Reports reflect the situation as reported
by the Member States to the European Commission in 2012
The situation in the MSs may have altered since then
Assessment of data and information reported by Member States on their
Preliminary Flood Risk Assessments and identification of Areas of
Potentially Significant Flood Risk under the Floods Directive
Member State Report: [UK] - [United Kingdom]
The main outcomes of the assessment were:
1. There are significant differences in how the requirements of the Floods Directive have been
implemented in the UK. In England and Wales Article 4 has been applied in terms of flooding
from ordinary (minor) watercourses and all other sources of local flooding, groundwater, and
pluvial, and Article 13.1.b to the main rivers and large raised reservoirs and sea water. In Scotland
Article 4 has been applied to all relevant types of flood, and in Northern Ireland, Article 4 has
been applied to fluvial and pluvial flooding. Finally in Gibraltar, Article 4 has been applied
specifically to sea water floods. There are also significant differences in the methodological
approaches between the 4 regions of the UK.
2. Article 4 has been applied in Scotland, Northern Ireland and Gibraltar for all types of flooding
considered as relevant. In England and Wales, this Article has only been applied by Lead Local
Flood Authorities (LLFA) who are responsible for pluvial and groundwater flooding, and from
minor watercourses which include ditches and streams not included as main rivers.
3. Article 13.1(a) has not been applied to any specific area or specific type of flood for any of the
RBDs in the UK.
4. Article 13.1(b) has only been applied to the UoMs in England and Wales and is applied to
floods from sea water, main rivers and large raised reservoirs. The only information reported to
WISE on methodologies was the overall approach, with the same text as reported for Article 4.
5. Only Scotland reported details (type and consequence) of significant historical flood events to
WISE. England (361) and Wales (113) (E&W) provided summaries of flood events instead of the
specific details requested. Northern Ireland also reported summaries of 27 flood events rather than
in the detail requested. In Gibraltar, a summary of 1 flood event was reported to WISE.
6. In Scotland, the location of future floods is primarily predicted and information on historic
floods is used to validate the predictions. In England and Wales, LLFAs used computer models to
generate information on future floods. In Northern Ireland, the future flood risk is assessed using a
GIS based Source – Pathway Receptor model that combines the output from predictive flood
models with a digital terrain model and a host of readily available receptor datasets. In Gibraltar,
no modelling for future flooding was undertaken and the assessment was based on largely
2 of 25
anecdotal evidence of past flooding. Only flooding from rainfall and storm surges from the sea
were considered to be significant for future risk assessments.
7. Adverse consequences were defined and considered, with regional differences in approach and
methodology.
8. All regions have given consideration to the impact of climate change on future flood risk.
Scotland, England, Wales and Northern Ireland have also considered the effect of building and
planning.
Question 0: Contextual information regarding the Member State.
There are 3 main regions in the main part of the UK: Northern Ireland (3 UoMs); Scotland
(1 main UoM (UK01) plus part of the UoM shared with England (UK02); and, England
and Wales (10 UoMs, one shared with Scotland). In addition Gibraltar (UKGI17) reported
a PFRA and APSFR. Information from 17 XML (two for UK02) files was included in the
WISE aggregation reports and was therefore used in the assessment. In addition, a number
of relevant documents were downloaded from the relevant national web sites to obtain
more detailed and specific information where necessary. The documents downloaded and
examined were:
Title Source
The National Flood Risk Assessment,
December 2011(of Scotland),
downloaded from the Scottish Environment
Protection Agency web site:
http://www.sepa.org.uk/flooding.aspx
Flood Risk Management (Scotland) Act 2009
Appraisal Method for Flood Risk Management
Strategies (not dated)
downloaded from the Scottish Environment
Protection Agency web site
http://www.sepa.org.uk/flooding.aspx
Flood Risk Management (Scotland) Act 2009
(FRM Act) National Flood Risk Assessment
Methodology, (not dated)
downloaded from the Scottish Environment
Protection Agency web site.
http://www.sepa.org.uk/flooding.aspx
Preliminary Flood Risk Assessment (PFRA),
Annexes to the final guidance Report –
GEHO1210BTHF-E-E, 2 March 2011.
downloaded from Environment Agency
(England) web site.
http://a0768b4a8a31e106d8b0-
50dc802554eb38a24458b98ff72d550b.r19.cf3.r
ackcdn.com/geho1210bthf-e-e.pdf
Flood Risk Management Plans: Guidance for
Risk Management Authorities in England and
Wales, A Living Draft, August 2013
downloaded from Environment Agency
(England) web site.
http://a0768b4a8a31e106d8b0-
50dc802554eb38a24458b98ff72d550b.r19.cf3.r
ackcdn.com/LIT_8649_4e4b09.pdf
Selecting and reviewing Flood Risk Areas for
local sources of flooding, Guidance to Lead
Local Flood Authorities, Flood Risk
Regulations 2009, (2010)
downloadable from www.defra.gov.uk or
www.cymru.gov.uk
Flooding in England: A National Assessment of
Flood Risk (2009)
downloaded from Environment Agency
(England) web site. http://www.environment-
agency.gov.uk/research/library/publications/10
3 of 25
8660.aspx
Preliminary Flood Risk Assessment and
Methodology for the Identification of
Significant Flood risk Areas December 2011,
Rivers Agency of Northern Ireland,
downloaded from web
http://www.dardni.gov.uk/final-pfra-report.pdf
Government of Gibraltar, Preliminary Flood
Risk Assessment, Final Report, January 2011
Downloaded from the web.
https://www.gibraltar.gov.gi/new/sites/default/f
iles/docs/Preliminary%20Flood%20Risk%20As
sessment%20Report.pdf
Flooding is a devolved responsibility for Wales, Scotland and Northern Ireland and so
there are significant differences in how the requirements of the Floods Directive have been
implemented in the UK. In England and Wales Article 4 has been applied in terms of
flooding from ordinary (minor) watercourses and all other sources of local flooding,
groundwater, and pluvial, and Article 13.1.b to the main rivers and large raised reservoirs
and sea water. In Scotland Article 4 has been applied to all relevant types of flood, and in
Northern Ireland, Article 4 has been applied to fluvial and pluvial flooding. Finally in
Gibraltar, Article 4 has been applied specifically to sea water floods. There are also
significant differences in the methodological approaches between the 4 regions of the UK.
Table 1 The application of Articles, 4, 13.1.a and 13.1.b in the Units of Management of
the United Kingdom Source: WISE Flood aggregation report “FD 1.1 Specific Areas to which each Article has been applied”
UoM Article 4 Article
13.1.a
Article
13.1.b
UK01 1 0 0
UK02_England 1 0 1
UK02_Scotland 1 0 0
UK03 1 0 1
UK04 1 0 1
UK05 1 0 1
UK06 1 0 1
UK07 1 0 1
UK08 1 0 1
UK09 1 0 1
UK10 1 0 1
UK11 1 0 1
UK12 1 0 1
UKGBNIIENB 1 0 0
UKGBNIIENW 1 0 0
UKGBNINE 1 0 0
UKGI17 1 0 0 Note: if the Articles have not been applied to or reported for any specific area, it is assumed that they have been applied to the
entire UoM. In which case the values in the table above will equate to 1. Values of zero for any Article or UoM indicate that that
the Article has not been applied to that UoM.
4 of 25
Table 2 Specific types of floods to which Article 4, 13.1.a and 13.1.b have been applied
Source: WISE Flood aggregation report: “FD 1.2 Types of flood to which each Article has been applied”
Article UoM Source * Mechanism * Characteristic * All types
**
Article 4 UK02_Englan
d, UK03,
UK04, UK05,
UK06, UK07,
UK08, UK09,
UK10, UK11,
UK12
"Ordinary
(minor)
watercourses
and all other
sources of local
flooding",
Groundwater,
Pluvial
Article 4 UKGBNIIEN
B,
UKGBNIIEN
W,
UKGBNINE
Fluvial, Pluvial
Article 4 UKGI17 Sea water Defence
exceedance
"Natural Flood"
Article 4 UK01,
UK02_Scotlan
d
yes
Article
13.1.b
UK02_Englan
d, UK03,
UK04, UK05,
UK06, UK07,
UK08, UK09,
UK10, UK11,
UK12
"Main Rivers
and large raised
reservoirs", Sea
water
* Source, mechanism and characteristics in quotation marks is source, mechanism and characteristics specified by member state
** No specific flood types were reported and it is assumed that Article 4 is applied to all flood types
Question 1: Are all the types of flood that might be reasonably expected in the Member State
included in the assessment of the risk of flooding under Article 4, Article 13.1(a) or Article
13.1(b)?
Source Included Not included but
Yes/No might be expected
Fluvial Yes
Pluvial Yes
Groundwater Yes
Sea water Yes
Artificial
water-bearing
infrastructure Yes
5 of 25
Other (provide
details in the
summary
below) No Yes
Summary assessment
There are 4 distinct regions in the UK relevant to this assessment: Scotland (UK01 and
part of UK02); England and Wales (UK03 to UK12); Northern Ireland (one report
covering the 3 UoMs); and Gibraltar. There are some differences in the reported
information.
In Scotland the National Flood Risk Assessment concentrated on rivers, coastal flooding
and heavy rainfall with some (though limited) consideration of the influence of
groundwater. No explicit mention is made of flooding from natural lakes (this is the other
options ticked above) or artificial water bearing infrastructure including reservoirs or
flooding from sewerage systems. Scotland has subsequently indicated that natural lakes
were part of the fluvial network for which flood extents were developed. Additionally,
flood risk information on a sub-set of Scotland’s sewerage systems was developed after the
NFRA but has been embedded into Scotland’s surface water flooding maps. It is not
considered a nationally significant source of flooding. Finally, groundwater was included
but is not considered a primary source of flooding; rather it is a contributing factor to other
types of flooding. Therefore, there is limited data on groundwater flooding that would
support further investigation.
In England and Wales, the Environment Agency has applied Article 13.1.b and is adapting
the current hazard and risk maps to the requirement of the Floods Directive (WISE
aggregation report). They are responsible for the main rivers, the sea and large raised
reservoirs. England and Wales have subsequently indicated that PFRAs were not produced
for river and coastal flooding as flood hazard and flood risk maps have been produced for
the whole of England and Wales instead of identifying APSFRs. Future work will produce
Flood Risk Management Plans for the whole of England and Wales. Lead Local Flood
Authorities have applied Article 4 to surface runoff, groundwater and ordinary watercourse
and any interactions these have with drainage systems and other sources of flooding
including sewers (except in terms of blockages or failures) and also excluding burst
(potable) water mains. Flooding from canals that are not main rivers should also be
included in the PFRA. The EA considers snowmelt as precipitation that would lead to
surface run-off and tsunamis as a form of sea flooding: it is not clear how the risk from
these latter two sources would have been assessed. No explicit mention is made of
flooding from natural lakes (this is the other options ticked above).
In Northern Ireland the main flooding sources considered were rivers, the sea, surface
water run-off and impounded water bodies (dams and reservoirs) though the latter source
was not conclusively assessed because of the lack of readily available information to make
this assessment: this shortfall will be dealt with in the future when new regulations will
6 of 25
enable the collection for the relevant data on reservoirs and dams. Groundwater flooding
was excluded because it was considered insignificant in Northern Ireland compared to the
other sources. There is also no explicit mention of natural lakes as a source of flooding.
In Gibraltar, 5 sources of flooding were considered: rivers, sea, surface run-off,
groundwater and infrastructure (flood defence) failure. There are no watercourses (rivers)
in Gibraltar and the risk from groundwater was considered as minimal (because of the
hydrogeology) and these sources were considered as representing no risk.
Table 3 Time period covered by different types of historic flood events
Source: WISE Flood aggregation report: “FD 2.0 Time period covered by historic flood events”
Source Total flood
events
Range of
years
2000
onwards
1950 to
1999
1900 to
1949
1800s Before
1800
Fluvial 92 1900-2009 19 27 46 0 0
Pluvial 15 1907-2010 5 2 8 0 0
Sea water 16 1949-2005 1 14 1 0 0
Artificial water-bearing
infrastructure
10 1990-2009 2 8 0 0 0
Other: Peat
Slide/Debris Flow/Bog
Burst
2 1979-2004 1 1 0 0 0
No data 13 1914-2008 5 7 1 0 0
7 of 25
Table 4 Types of historical significant flood events and types of reported consequences
Source: WISE Flood aggregation report: “FD 2.1 Types of historical significant flood events”
Member
State
Article
Source
Mechanism
Characteristics Number of
Historical
floods
Number of
flood events with no
data
Number with reported consequences
Human
Health
Environment Cultural
Heritage
Economic
Activity
UK Article 4 no data 13 0 14 13 13 13
UK Article 4 "Peat Slide/Debris
Flow/Bog Burst"
2 0 2 2 2 2
UK Article 4 Artificial water-bearing
infrastructure
10 0 10 10 10 12
UK Article 4 Fluvial 92 0 95 92 92 124
UK Article 4 Pluvial 15 0 16 15 15 19
UK Article 4 Sea water 16 0 16 16 16 20
Table 5 Types of potential future significant flood events and types of consequences
Source: WISE Flood aggregation report: “FD 3.1 Types of potential future significant flood events”
Member
State
Article
Source
Mechanism
Characteristics Number of
Potential
Future floods
Number
of flood events
with no data
Number with reported consequences
Human
Health
Environment Cultural
Heritage
Economic
Activity
UK Article 4 "Main rivers" Natural exceedance Medium onset
flood
24 0 24 24 24 24
UK Article 4 "Ordinary (minor)
watercourses"
Natural exceedance Flash flood 2 0 2 2 2 2
UK Article 4 "Ordinary (minor)
watercourses"
Natural exceedance Medium onset
flood
11 0 11 11 11 11
8 of 25
UK Article 4 Artificial water-
bearing infrastructure
Defence or
infrastructural failure
Flash flood 3 0 3 3 3 3
UK Article 4 Groundwater Natural exceedance Medium onset
flood
14 0 14 14 14 14
UK Article 4 Pluvial Defence exceedance Medium onset
flood
1 0 1 1 1 1
UK Article 4 Pluvial Natural exceedance 2 0 2 2 2 2
UK Article 4 Pluvial Natural exceedance Flash flood 1 0 1 1 1 1
UK Article 4 Pluvial Natural exceedance Medium onset
flood
134 0 134 134 134 134
UK Article 4 Sea water Defence exceedance "Natural Flood" 1 0 1 1 1 1
9 of 25
Question 2a: What aspects required by Article 4 were not considered in the application of
Article 4?
Has Article 4 been applied?
Yes, information has been reported on this aspect
Summary assessment
This Article has been applied in Scotland, Northern Ireland and Gibraltar for all types of
flooding considered as relevant. In England and Wales, this Article has only been applied
by Lead Local Flood Authorities (LLFA) who are responsible for pluvial and groundwater
flooding, and from minor watercourses which include ditches and streams not included as
main rivers (which are the responsibility of the Environment Agency of England and
Wales who are applying Article 13.1.b for this type and some other types of flood).
Based on the information reported to WISE, in Scotland all the expected aspects have been
included in the PFRA.
In England and Wales the Environment Agency provided the LLFAs guidance on what
was required in a PFRA. Based on the guidance and the WISE report (and not an example
of a PFRA produced by a LLFA) it seems that most aspects would have been included.
However, there may be some limitations in the assessment of the risk from groundwater
flooding as the dataset used (Areas Susceptible to Groundwater Flooding) is quoted not to
be interpreted as identifying areas where groundwater is actually likely to flow or pond:
rather it should be used to identify where further studies would be useful. England and
Wales has subsequently indicated that further assessment of groundwater flooding is being
considered as a result of flooding events that occurred in 2014. In terms of surface water
flooding there was also no readily available or derivable information about the
effectiveness of existing man made infrastructure (drainage). LLFAs are also response for
assessing the hazard and risk from minor water courses. Some of these may have been
covered by existing datasets but there may also have been gaps in the aspects such their
geomorphological characteristics that were not included.
For the PFRA in Northern Ireland most aspects have been considered. There was an initial
consideration of the geomorphological characteristics of watercourses. Northern Ireland
has subsequently indicated that it was not possible to develop a practicable broad-scale
approach that would be sufficiently robust to support a meaningful assessment of the
potential for geomorphological activity to change the future flood risk from the many
hundreds of rivers under consideration. The effectiveness of flood defences was also
ignored in the indicative (strategic) flood models used to assess the potential adverse
consequences of future floods because of the uncertainty associated with the actual levels
of protection offered by the existing defences (river walls, flood banks, culverts etc.). This
approach was adopted to ensure that communities located behind the existing major flood
defence systems were identified as areas of potential significant flood risk and thereby
create the opportunity to develop detailed predictive flood models and produce hazard and
risk maps that illustrate the estimated level of protection provided to the areas by the
defences.
The PFRA for Gibraltar also covers all aspects that are relevant to the characteristics of
water bodies in Gibraltar.
10 of 25
Question 2b: What aspects required by Article 4 were not considered when producing an
assessment of the risk of flooding under Article 13.1(a)?
Has Article 13.1(a) been applied?
No, it is explicitly stated that this Article has not been applied
Summary assessment
This Article has not been applied to any specific area or specific type of flood for any of
the RBDs in the UK.
Question 3: What aspects required by Article 4 were not considered when producing Flood
Hazard Maps and flood risk maps, and Flood Risk Management Plans under Article 13.1(b)?
Has Article 13.1(b) been applied?
Yes, information has been reported on this aspect
Summary assessment
In the UK, this Article has only been applied to the UoMs in England and Wales (part of
UK02 and UK03 to UK12), and is applied to floods from sea water, main rivers and large
raised reservoirs. Large reservoirs are defined by a size criterion of 25,000 m3 capacity
though this is to be decreased to 10,000 m3 capacity on implementation of new legislation.
The Environment Agency of England and Wales will produce flood hazard and risk maps
and flood risk management plans for flood risk from main rivers, large raised reservoirs
and the sea by adapting the existing maps and plans to meet the requirements of the Floods
Directive. The only information reported to WISE on Article 13.1.b methodologies was on
the overall approach: this was the same text as reported for Article 4 and only describes the
respective role of the EA and Lead Local Flood Authorities. A search of the Environment
Agency of England and Wales’ web site did not locate any detailed methodological reports
on the basis of existing flood hazard and flood risk maps. The statement that existing maps
will be adapted to meet the requirements of the Floods Directive implies that the current
maps do not cover all aspects outlined in Article 4. In addition no specific information was
found on how the risk from large raised reservoirs would be assessed.
11 of 25
Question 4: What are the types of floods considered/not considered within the auspices of the
Floods Directive?
Summary assessment
Considering the UK as a whole, fluvial, pluvial, groundwater, sea water and floods from
artificial water bearing infrastructure have been considered but there are significant
regional differences.
Peat slide/debris flow/ bog burst floods were reported (in WISE) for Scotland (UK01) as
historic but not potential future flood event. Scotland has subsequently indicated that the
lack of available, detailed and reliable information on these types of flood prevented them
from being included in the future flood assessment. Historic flooding in Scotland has also
resulted from snow melt and ice blockages but again these were not included in the future
flood assessment due to a lack of information and because they are infrequent and not
considered significant. In Scotland the National Flood Risk Assessment (2011)
concentrated on rivers, coastal waters and pluvial flooding with a “further consideration of
the influence of groundwater”. However in the Scotland report (Appraisal method for
Flood Risk Management Strategies First edition) it is stated that “Groundwater flooding
will not be considered within the appraisal process. Accurate data relating to groundwater
risk in Scotland is not currently available, and there is uncertainty related to the potential
for groundwater to cause flooding. It is understood that groundwater issues can exacerbate
flooding from other sources however, the levels of flooding attributed to groundwater are
uncertain.”
Raised reservoirs over 10,000 m3 capacity (artificial water bearing structures) are included
in England Wales but not in Northern Ireland (because of a lack of information even
though they are considered as being potentially significant) or in Scotland (no reason
found). Scotland has subsequently indicated that this was due to a lack of available and
reliable information prior to submission. It also noted that the Reservoirs (Scotland) Act
2011 includes a responsibility for SEPA to assign a risk designation to all reservoirs over
10,000 m3 capacity. This will be based on the potential adverse consequences of an
uncontrolled release of water and the probability of such a release. The outputs from these
assessments will be considered for inclusion in future reporting cycles.
Canals are also considered in England and Wales. In England and Wales a differentiation
is made between main rivers and ordinary water courses (e.g. stream, ditches and sluice) in
terms of fluvial flooding for which, respectively, the Environment Agency of England and
Wales and the Local Lead Flood Authorities (municipal authorities) are responsible (WISE
report). Scotland has subsequently indicated that canals were not included in the
assessment for Scotland as flood risk from canals is not considered significant and little
information was available, Flooding from sewers does not have to be considered in
England and Wales unless wholly or partly caused by rainwater entering or otherwise
affecting the system (WISE).
12 of 25
Groundwater flooding is also considered to be insignificant in Northern Ireland (PFRA
report) compared to other sources, as confirmed by a desktop review of hydrogeology and
flooding history that demonstrated no areas at significant risk from groundwater flooding.
In Gibraltar (UK17) (PFRA document) only two sources of potential flooding (pluvial and
sea water) were considered to represent a risk (i.e. significant): there are no surface
watercourses and the hydrological characteristics of the groundwater aquifers led to the
conclusion that they represented no risk. A residual risk was considered to arise from sea
flood defence failure during extreme tidal events.
Question 5: What were the criteria used to define the historical significant floods and what
were the reasons for not including some types of flood that occurred in the past?
Summary assessment
Only Scotland reported details (type and consequence) of significant historical flood
events to WISE. Historic flood events were collated from a number of sources including
SEPA data and newspaper records. 15,000 individual flood events were found covering all
of Scotland. An impact score was assigned to each event ranging from 0 (very low impact)
to 4 a very high impact. Impact was based on the effects on receptors including Human
Health, Economic Activity, Environment and Cultural Heritage. Threshold criteria (not
reported or found) were associated with the impacts on each receptor, the exceedance of
which indicated significance. Any event which has a very high impact (4) was deemed to
be significant.
England (361) and Wales (113) (E&W) provided summaries of flood events rather than
details, as permitted in this reporting cycle. Defra has subsequently indicated that this was
because information on past flood events was not readily derivable. The reported
information for E&W is for the PFRAs undertaken by the Lead Local Flood Authorities
(e.g. county council and unitary administrative authorities) which have responsibility for
flooding from defined sources such as pluvial and groundwater. The Environment Agency
(EA) of E&W has responsibly for other sources of flooding such from main rivers and sea
water and they have applied Article 13.1.b and hence are not producing PFRAs but are
going straight to the development/revision of existing Flood Hazard (FH) and Flood Risk
(FR) Maps. The Environment Agency (EA) provided guidance to the LLFAs on the
production of PFRA which listed a number of sources of historic flood information. It is
not clear how (or if) the EA used the historic information in the development of the FH
and FR maps as their method seems to be solely based on modelling. The relevant
information was sought for in a number of EA publications downloaded from their web
site including “National Assessment of Flood Risk”. In terms of the LLFAs, the factors
used to determine the significance of any harmful consequences of historic flood events
included those that were significant on a national scale; how memorable the event was;
scale of the flooding and consequences and the level of response; severity of impacts; and
13 of 25
on whether the quality of the information was sufficient to determine if there were
significant harmful consequences.
Northern Ireland also reported summaries of 27 flood events rather than in detail, as
permitted within this reporting cycle. In Northern Ireland a library and media review of
flood events was undertaken to establish the extent of major floods events dating back to
early 1900’s. Since 1980 floods have been recorded by aerial photography. The Flood risk
associated with post 1980 flood events has been assessed using a GIS application which
calculated key Flood Risk Indicators associated with their adverse consequences to Human
Health, economic activity, Environment and cultural heritage. No information was found
on what criteria equated to a historic event being significant in Northern Ireland.
In Gibraltar, information on past floods was found from a wide range of sources including
Government departments, museums and utility companies. A summary of 1 flood event
was reported to WISE. There was no information on what equated to a historic significant
floods though groundwater floods were not considered in the PFRA because there were no
recorded events from this source. No information was found from the other parts of the
UK on the basis of exclusion of specific flood types from the consideration of historic
flood events.
Question 6: What methods and criteria were used to identify potentially significant future
floods and what were the reasons for not including some types of potential future floods?
Summary assessment
In Scotland the location of future floods is primarily predicted. Information on historic
floods is used to validate the predictions. The 1 in 200 year (annual exceedance
probability of 0.5%) indicative river and coastal flood extents were used and these were
integrated with national (Scottish) pluvial and groundwater datasets. A systematic 1km2
grid approach was used in assessing flood hazard to defined receptors from fluvial, coastal
and pluvial flood sources. A groundwater factor was also applied for areas which were
classified as having a high or very high susceptibility to flooding. In general however the
focus of the National Flood Risk Assessment (NFRA) was on fluvial, pluvial and coastal
flooding rather than that from groundwater. The significance of the records of historic
flood events was assessed using a scoring method incorporating the impact, source and
reliability of the event. This data was then used to validate the NFRA grid output ensuring
that significant historic events were used in the determination of Potentially Vulnerable
Areas. Because of some uncertainty in the methods for assessing flood risks, a manual
review was undertaken to take account of any uncertainties within the grid outputs.
In terms of the sources of flooding (pluvial, groundwater and ordinary watercourse) for
which the LLFAs are responsible in England and Wales, computer models were used to
generate information on future floods. In terms of surface run-off the derived national
datasets included areas susceptible to surface water flooding and the flood map for surface
14 of 25
water. The assessment was based on flooding to a depth of 0.3 metres by a rainfall event
with a chance of 1 in 200 of occurring in any given year (equivalent to 'in the order of' 1 in
100 chance of flooding). These datasets were supplemented by locally agreed surface
water information which best represented local conditions. For groundwater a national 1
km2 grid datasets was used where no local information was available. In terms of ordinary
water course there were no datasets that dealt solely with this source and so national
surface run-off datasets were used when possible supplemented by any local information.
No specific information relating to the Environment Agency’s methods for assessing the
risk of flooding from coastal waters, main rivers and from raised reservoirs was found in
spite of extensive search on the relevant web sites.
In Northern Ireland the future flood risk is assessed using a GIS based Source – Pathway
Receptor model that combines the output from predictive flood models with a digital
terrain model and a host of readily available receptor datasets. The assessment of the
potential adverse consequences of flooding is based on three different probability events
(low, medium and high) for each of the flood sources. By producing flood outlines with
different return periods it was possible to ‘annualise’ Flood Risk Indicator values to
produce estimates of the adverse effects that best represent the true long term annual
average. The AEP of the events used in the assessment for each source is fluvial: 10%, 1%
and 0.1%, coastal; 10%, 0.5% and 0.1% and pluvial 10%, 0.5% and 0.1%. No information
was reported on the methods for groundwater and artificial water bearing infrastructure.
In Gibraltar no modelling for future flooding was undertaken and the assessment was
based on largely anecdotal evidence of past flooding. Only flooding from rainfall and
storm surges from the sea were considered to be significant for future risk assessments.
Question 7: What types of flood were considered but not assessed as being significant, and what
were the reasons given?
Summary assessment
In Scotland the significance of historic floods was assessed by assigning an impact score
to each event ranging from 0 - 4, where 0 indicates a Very Low impact event and 4
indicates a Very High Impact event. This allowed areas historically prone to flooding to be
highlighted. An impact threshold matrix was developed to ensure consistency when
assigning impact scores. The matrix contained the most common examples of each impact
for each receptor. Event descriptions must include the threshold criteria in order to be
designated as a significant event. A score multiplier was added after the impact scoring.
This took into account the age of the flood event and ensured that events were more fairly
scored given the changes in, for example, building standards. Any event which had a Very
High Impact was deemed to be Significant. Where significant flood events occurred within
an APSFR, it was considered that significant adverse consequences of similar future flood
events may be envisaged. The PFRA in Scotland concentrated on flooding from rivers, the
coast and heavy rainfall with a further consideration of the influence of groundwater.
15 of 25
There is no mention of potential floods from impounded water bodies (e.g. reservoirs or
canals) or natural lakes or specifically of flooding from sewers. No reasons were found
why they were not considered. Scotland has subsequently indicated that natural lakes were
part of the fluvial network for which flood extents were developed.
In England and Wales reservoirs below 10,000m³ in capacity were considered as unlikely
to present significant flood risks in the context of implementing the requirements of the
Floods Directive. In addition the Lead Local Flood Authorities (LLFAs) do not need to
assess flooding from sewers, unless wholly or partly caused by rainwater or other
precipitation entering or otherwise affecting the system. Floods of raw sewage caused
solely, for example, by a sewer blockage do not fall under the national Regulations
implementing the Floods Directive. The Regulations also do not apply to floods from
water supply systems, e.g. burst water mains, Snow melt and tsunamis. Snowmelt would
count as precipitation and so could lead to surface runoff. Tsunamis are considered as a
form of flooding from the sea. LLFAs also did not include past floods of a kind that are not
likely to occur now due to improvements in drainage or flood risk management measures.
In Northern Ireland an initial review of historical flooding was undertaken to scope the
potential risk from all flood sources. From this it was concluded that the main flood
sources likely to give rise to significant flooding were rivers, the sea, surface water runoff
and impounded water bodies (such as dams and reservoirs). However, the flood risk from
impounded water bodies was not conclusively assessed in the PFRA as there was at the
time insufficient ‘available or readily available’ information to conduct a robust
assessment of the risk from this source. The reason for this lack of information is that NI
does not have legislation for the management of reservoir safety and as a consequence the
owners of impoundments have not been required to collate such information as would be
necessary to assess the potential risk of their failure. NI will address this risk through the
introduction of new reservoir safety legislation. It is stated that Groundwater flooding is
insignificant in Northern Ireland compared with fluvial, coastal and pluvial flooding. As a
consequence it was decided not to explore the development of predictive flood models for
this source.
The only sources of flooding considered to be of potential significance in Gibraltar were
from the sea and from surface water run-off. Neither of these was considered to represent a
significant risk. Flooding from the two groundwater bodies in Gibraltar was also
considered but because of their hydrological characteristics they were not considered as
being relevant. A strategic assessment of the drainage and sewerage network within the
Gibraltar RBD was additionally used to assess the level of flood risk.
Question 8: What types of flood were not considered at all, and why?
Summary assessment
16 of 25
In Scotland it appears that flood from impounded water bodies (e.g. reservoirs or canals),
natural lakes and from sewers were not considered. No reasons for this were found. In
England and Wales all types of flood except from natural lakes seem to have been
considered. England and Wales has subsequently indicated that it is included in the flood
maps but is not considered a separate source of flooding. From the reported information
for Northern Ireland it is not clear whether canals are included in and considered as part of
impounded water bodies. Natural lakes such as Lough Neagh were also not mentioned.
Flooding from sewers is also not described as a potential source of flooding. Rivers do not
occur on Gibraltar, hence this source was not considered. It is not known whether or not
impounded water bodies occur in Gibraltar; no mention was made of them in the WISE
reports.
Question 9: What criteria were used to define an adverse consequence?
Summary assessment
In Scotland the following receptors of flooding were considered:
Human Health (A) People: No. of People/social flood vulnerability;
Human Health (B) Community: Community facilities that could cause community
disruption if affected by flooding
Economic Activity (A) Businesses: No. of business properties and the estimated
damages;
Economic Activity (B) Transport: Roads, railways and airports;
Economic Activity (C) Agriculture: Agricultural land and forestry areas;
Environment: Designated Areas and the susceptibility and resilience of the
species/habitats to the impacts of flooding;
Cultural Heritage: the importance of cultural sites exposed to flooding.
The criteria that defined an adverse consequence on each receptor were not reported to
WISE. Scotland has subsequently indicated that flood risk was calculated as a product of
likelihood, hazard, vulnerability, exposure and value.
The other aspects required to be considered under Article 4.2.d (hydrological and
geomorphological characteristics; effectiveness of existing manmade flood defence
infrastructures; climate change; future land planning) were included in the PFRA.
In England and Wales Lead Local Flood Authorities (responsible for pluvial, groundwater
and minor watercourse flooding) used the following flood risk indicators to assess the
potential adverse consequences of future flooding. Human health; number of people
affected, number of critical services; Economic activity; number of non-residential
properties, infrastructure network (length of roads and rail), and area of agricultural land;
Environment and heritage, the consequences of pollution, the impact on internationally and
nationally designated environmental sites, and the impact on internationally and nationally
17 of 25
designated heritage assets. It is assumed that “consequences of pollution” might include
any effect on water body status (i.e. WFD status).
Elements representing the topography, the position of watercourses and their general
hydrological and geomorphological characteristics, including floodplains as natural
retention areas were also included in the modelling for future potential floods. The position
of populated areas, areas of economic activity were also described. The criteria that
defined an adverse consequence on each receptor were not reported to WISE. No
equivalent information was reported to WISE for the other sources of floods for which
England and Wales is applying Article 13.1.b. However, as the authority responsible for
these other sources of flooding (Environment Agency of England and Wales) provided
guidance to the LLFAs in producing PFRAs, it seems likely that the same approach and
criteria would have been applied.
In Northern Ireland a GIS application was developed to combine the flood extent outlines
with a wide range of receptor datasets. Embedded within the application is a Flood Risk
Query Tool which applies algorithms to the data to quantify the flood risk in terms of flood
risk indicators. A broad range of flood risk indicators have been generated to measure the
adverse impact of potential flooding on groups of receptors on an average annual basis.
For example there are Flood Risk Indicators that quantify the annual flood risk in terms of
the number of people and their vulnerability, the number of properties (and their various
types), the number of key services, the length of key transportation infrastructure flooded,
the economic damages, the areas of environmental sites inundated, the number of
Integrated Pollution Prevention and Control sites and the number of nationally important
cultural heritage sites (i.e. Listed Buildings, Gardens, Sites and Monuments Records and
Sites of Archaeological Interest). An example of a key flood risk indicator is the
Aggregated Average Annual Damage (AAAD). This is the estimated average economic
damages arising from all sources of flooding which, taken over the very long-term, is
likely to occur on an annual basis.
The Flood Risk Indicators are supported as necessary by information on the vulnerability
of particular receptors. For example, UK census data was used to identify more vulnerable
populations, such as conglomerations of elderly population. The spatial distribution of the
Economic Deprivation Index computed by the Northern Ireland Statistical Service was
computed for flooded properties and used in the assessment of the vulnerability of people
to flooding. The criticality of key infrastructure and designated environmental sites
susceptible to flooding was determined through a broad ranging consultation exercise that
included the owner/operators of the asset owners and the NI Environment Agency. The
criteria associated with the Flood Risk Indicators that defined an adverse consequence on
each receptor were not reported to WISE.
In Gibraltar the criteria used to identify and assess significant flood risks included, but
were not limited to public health impacts, damage to property and infrastructure, number
of people affected along with the impacts of pollution. These were considered to be the
main indicators that are applicable to Gibraltar. Gibraltar did not identify any areas that
18 of 25
they considered to be at a significant flood risk but areas of land were identified that might
become inundated during flooding events from storm (sea) surges or heavy rainfall, but
where significant damage is unlikely to occur.
Question 10: What adverse consequences were excluded or not considered, and what were the
reasons for their exclusion?
Summary assessment
None seem to have been excluded in Scotland’s PFRA (WISE and downloaded
documents).
In England and Wales the LLFAs may not have considered some of the issues identified
under Article 4.2(d) in some of the future flood information where it was considered not
appropriate, or the information was not available, for assessment of local flood risk. For
example, the broad scale modelling of local flood risk has limited or no readily available
or derivable information about the effectiveness of existing manmade infrastructure. In the
case of surface water infrastructure it is usually a matter of very small local interventions,
including elements of the drainage and pumping network, or even variations in kerb
heights or the camber of a road that can influence the effectiveness of drainage.
For future floods such as the Areas Susceptible to Groundwater Flooding, and some local
future flood information, no automatic analysis was available about the position of
populated areas, and areas of economic activity as contained within the Environment
Agency's National Receptor Dataset. For groundwater LLFAs made their own assessment
of the impacts from local knowledge or overlaying with other maps of spatial information.
The influence of geomorphology was considered in the PFRA (PFRA document) for
Northern Ireland and an activity index was generated and based on land cover, drift
geology and stream-power with validation based on inspecting digital terrain /
photography images. Reaches with the greatest potential for geomorphological activity
that might affect flood risk were highlighted. However, the analysis was a broad-scale
approach and more site specific detailed studies of deposition and flood risk would be
required. Given the uncertainty associated with the approach used it was concluded that
geomorphology should not be considered further when assessing the potential
consequences of future floods. However, geomorphology data will be taken into account
when options are being considered for flood risk management plans.
Flood defence infrastructure has been ignored in the predictive modelling of future
flooding in Northern Ireland. This is a precautionary approach because there are
uncertainties regarding the levels of protection that flood defences would provide in
practice given the detailed information and analysis required for proper assessments.
19 of 25
There is little detailed information in the PFRA downloaded document for Gibraltar. The
text implies that adverse impacts on human health, economy, environment and cultural
heritage have been considered.
Question 11: What methods were used to identify and quantify potential future adverse
consequences and impacts?
Summary assessment
In Scotland a 1 in 200 year indicative river and coastal flood extents were used for the
PFRA. These represent the floodplains as natural retention areas. National pluvial and
groundwater datasets were also developed and integrated into the PFRA. An annual
exceedance probability factor of 0.5 was applied. Pluvial flooding extents were generated
using a 0.1 m and 0.3 m depth contours for use within the assessment. Each receptor was
assessed in terms of exposure to flood hazards, and also the characteristics of receptors
(i.e. the value/vulnerability to impacts of flooding). A 1km² grid approach was adopted
where grid cells were attributed with a risk score depending on the characteristics of the
receptors within the cell. A grid output was created for fluvial, coastal and pluvial flood
sources, for each receptor category, these were combined to provide a total score per cell.
A groundwater factor was then included for areas which had been classified to have a High
or Very High susceptibility to groundwater flooding.
A quantitative method was then used for translating the grid output to a higher geographic
level called the sub catchment unit (SCU). This summed the scores of all the cells within
each SCU and categorised the SCUs from Very Low to Very High. Additional information
only relevant or applicable at the catchment scale was then included in the analysis.
Flood defences were considered in a 2 phase process: the 1st phase identifies the
protection offered by defences; the 2nd phase is a manual, qualitative assessment of the
area behind a defence and the potential benefit offered- both are carried out at the SCU
level. The results of the assessment of historic floods was used to validate the grid output,
ensuring that significant past flood events have been identified and analysed to inform the
categorisation of SCUs and the definition of Potential Vulnerable Areas (PVA). All SCUs
categorised as Very High, High or Medium categories were included as PVAs.
The receptor groups used in the PFRA for the identification of flood risk areas in Scotland
were: 1. Human Health (A) – People (No. of Residential Properties and the social
vulnerability of the area); 2. Human Health (B) - Community (Important facilities that
could cause community disruption if affected e.g. schools, hospitals); 3. Economic
Activity (A) - Businesses (No. of business properties and the estimated weighted annual
average damage related to the property); 4. Economic Activity (B) - Transport (Roads,
railways and airports); 5. Economic Activity (C) - Agriculture (Agricultural land and
forestry areas); 6. The Environment (Areas designated for natural heritage purposes and
their vulnerability to flooding); and, 7. Cultural Heritage (Cultural sites such as UNESCO
20 of 25
World Heritage Sites). The receptors were assessed using risk categories from Very Low
to Very High.
A large range of thresholds and methods have been tested to ensure that that the resulting
categorisation most accurately represents flood risk in Scotland. These are described in
detail in “Flood Risk Management (Scotland) Act 2009 (FRM Act), National Flood Risk
Assessment Methodology, Scottish Environment Protection Agency”, downloaded from
internet.
The main source of information about future floods in England and Wales is in the form of
maps produced by computer models. National maps of surface water flooding called the
Areas Susceptible to Surface Water Flooding (AStSWf) and the Flood Map for Surface
Water (FMfSW) include elements representing the topography, the position of
watercourses and their general hydrological and geomorphological characteristics,
including floodplains as natural retention areas.
The position of populated areas, areas of economic activity are described by the
Environment Agency's for England and Wales National Receptor Dataset, and analysis of
FMfSW and AStSWF were informed by this. The FMfSW contains two rainfall events,
divided into two depth bandings: 1 in 200 rainfall and 1 in 200 rainfall deep, as well as 1 in
30 rainfall and 1 in 30 rainfall deep. The AStSWF dataset contains one rainfall event, with
three susceptibility bandings: less, intermediate and more.
Some Local Lead Flood Authorities (responsible for pluvial, groundwater and flooding
from minor water course etc) were also able to use other future flood scenarios produced to
assess the impact of local sources of flooding from past studies of specific areas. National
maps of river and sea flooding were available in addition to the surface water maps to
assess potential areas where different sources of flooding could interact. Information about
potential groundwater flooding was provided from Areas Susceptible to Groundwater
Flooding map to help assess areas where this type of flooding could pose an additional
risk. Using the available maps and data sets, LLFAs were able to assess the potential
adverse consequences of future flooding.
The Environment Agency of England and Wales provided a very broad scale map showing
groundwater flood areas on a 1km² grid, called "Areas Susceptible to Groundwater
Flooding". This was deemed sufficient for the PFRA where no local information exists.
There are no Environment Agency products that deal solely with flooding from ordinary
watercourses, however the national surface water maps, and the Flood Map for rivers and
sea (for which the Environment Agency of England and Wales is responsible) contain
some relevant information, and so were included in PFRAs. Where additional information
about future flooding from ordinary watercourses exists locally, it was recorded in the
PFRA.
In England and Wales Defra and the Welsh Assembly Government provided guidance
(Selecting and reviewing Flood Risk Areas for local sources of flooding: Guidance to
Lead Local Flood Authorities Flood Risk Regulations 2009, Department for Environment,
21 of 25
Food and Rural Affairs, 2010, downloaded from the internet) to the LLFAs on the
indicators and thresholds to be used to determine the indicative Flood Risk Areas
equivalent to where there is a significant flood risk in their area. Flood Risk Areas are
where flood hazard and risk maps and flood risk management plans compliant with the
Floods Directive will be prepared. In determining the criteria, the consequences of
flooding to people are considered the most important. For example, the threshold for the
number of people (based on number of residential properties x 2.34) at risk was set at
30,000 for England and 5,000 for Wales (because of predominantly smaller settlements in
Wales), and for the number of critical services (including schools, hospitals, nursing
homes, power and water services) 150 in England and 25 in Wales although number of
people is the deciding threshold for indicative Flood Risk Areas. The assessment was
based on flooding to a depth of 0.3 metres by a rainfall event with a chance of 1 in 200 of
occurring in any given year (equivalent to 'in the order of' 1 in 100 annual probability of
flooding).
In Northern Ireland it was considered to be not appropriate to identify and assess ‘potential
future significant floods’ as this presupposes that only floods exceeding a particular
magnitude are deemed to be significant and takes no account of the periodicity of floods. It
was thought more appropriate to identify the significance of the total flood risk in discrete
areas in a manner that takes account of the adverse consequences of the whole spectrum of
floods which range in magnitude and periodicity. The future flood risk is assessed using a
GIS based Source – Pathway Receptor model that combines the output from predictive
flood models with a digital terrain model and a host of readily available receptor datasets.
The assessment of the potential adverse consequences of flooding is based on three
different probability events (low, medium and high) for each of the flood sources. By
producing flood outlines with different return periods it was possible to ‘annualise’ Flood
Risk Indicator values to produce estimates of the adverse effects that best represent the
true long term annual average.
The Annual Exceedance Probability of the events used in the assessment for each source is
fluvial: 10%, 1% and 0.1%, coastal; 10%, 0.5% and 0.1% and pluvial 10%, 0.5% and
0.1%. The GIS application identifies the receptors that are spatially intersected by flood
outlines for the high, medium and low probability flood events for each of the flood
sources. Embedded within the application is a Flood Risk Query Tool which applies
algorithms to the data to quantify the flood risk in terms of flood risk indicators.
A broad range of flood risk indicators have been generated to measure the adverse impact
of potential flooding on groups of receptors. The flood risk indicators included the:
Number of different building types located within any flood outline; Number of flooded
key services split into different categories and totalled; Number of people at risk (number
of flooded residential buildings times 2.5 people per dwelling); Number of IPPC sites
flooded and the area of IPRI site polygons flooded; Length of key infrastructure flooded
(roads); Area of flooded buildings; Area of flooded ASSI; Vulnerability based on census
22 of 25
data; Economic Deprivation; Property damages of flooded buildings; and Agricultural
damages.
The long-term annual average values of all these indicators was computed for fluvial,
coastal and pluvial flooding by integrating the indicator (i.e. damage) versus probability
curves. These quantitative indicators are used in whole or in part to assess the potential
flood risk in the broad categories required by the Directive; i.e., human health, economic
activity, cultural health and the environment. The suite of flood risk indicators are
measured in 1km grid squares. By computing the flood risk indicators at this spatial level
it is possible to use them to compare and contrast the risk across Northern Ireland at a
broad community scale.
There has been no modelling of flooding in Gibraltar and therefore the information used in
the PFRA has been derived from an assessment of the water bodies in the Gibraltar RBD
and from anecdotal evidence obtained by the Department of the Environment.
Question 12: What long term developments were considered, what methods were used and what
were the expected impacts on the occurrence of potentially significant future floods?
Summary assessment
In Scotland a project was undertaken to assess the vulnerability of Scotland’s river
catchments and coasts to the impact of climate change. The method for rivers used an
estimate of a catchment’s sensitivity to climatic change then combined it with information
on climatic hazard in order to estimate the risk in terms of the impacts on peak river flows.
Catchment sensitivity (response type) was estimated from each catchment’s properties.
This approach is intended to be scenario-neutral (i.e. based on catchment response rather
than the time-varying outcome of individual (climate change) scenarios) in order to
provide a strong base assessment of the potential impact of climate change and thus secure
confidence in setting future objectives and measures to manage flood risk. The coastal
approach included the definition of climate change predictions, coastal behaviour systems
and associated sensitivity analysis, identification of assets exposed to hazards and finally
an assessment of coastal vulnerability. A factor relating to the potential impacts that
climate change would cause was applied to each catchment unit. The factor is based on the
increase in economic costs which would be expected due to a greater flooding depth to
identified receptors. The factor does not include additional receptors being placed in the
floodplain.
Future strategic developments are also considered in Scotland. These were obtained from
the Scottish Government’s long term spatial strategy for Scotland's development. This sets
out a commitment to an integrated approach to water management including flood risk
management. The potential increase in flood risk as a result of climate change is
recognised and recommends that available flood maps are utilised to inform decisions on
23 of 25
the appropriate locations of new build developments. Data identifying the locations of
these strategic areas of development has been created. The types of developments included
are national scale and include regeneration projects, large residential developments and
infrastructure improvements. This data has been used in combination with other
information such as climate change impacts, to aid in the definition of potential vulnerable
areas.
Studies have been undertaken to develop information (Key Projections) and implications
for flood risk for each River Basin District (RBD) in England and Wales on climate
change and long term developments based on the most recent UK Climate change
predictions study, UKCP09. The Lead Local Flood Authorities have included and used the
projections relevant to the RBD and its area to inform the PFRA on the sources of flooding
they are responsible for. It is implied in the “Flooding in England: A national assessment
of flood risk” report (there is an equivalent report for Wales) that the same approach is
used by the Environment Agency in the assessment of flood risk from the sources for
which it is responsible.
All English PFRAs produced by the LLFAs include a short description of the current
planning policy for England, which aims to prevent new building and infrastructure
development from increasing flood risk. Planning policy for England is likely to be
revised in 2012. In England, Planning Policy Statement 25 (PPS25) on development and
flood risk aims to "ensure that flood risk is taken into account at all stages in the planning
process (the process by which developers obtain permission to carry out development) to
avoid inappropriate development in areas at risk of flooding, and to direct development
away from areas at highest risk.
Where new development is exceptionally necessary in such areas, policy aims to make it
safe and sustainable without increasing flood risk elsewhere and where possible, reducing
flood risk overall." Local Planning authorities administer the planning process and rely on
statutory consultees such as the Environment Agency and Water Companies as well as
Strategic Flood Risk Assessments for their area (SFRAs) to inform their decisions about
potential flood risks. Adherence to Government policy should ensures that new
developments do not increase local flood risk. In exceptional circumstances the Local
Planning Authority may accept sustainable development that increases flood risk, usually
because of the wider benefits of a new or proposed major development. Any exceptions
would not be expected to increase risk to levels which are "significant" (in terms of the
Government's criteria). In Wales, Technical Advice Note 15 (TAN15) on development and
flood risk sets out a precautionary framework to guide planning decisions. The overarching
aim of the precautionary framework is "to direct new development away from those areas
which are at high risk of flooding."
In Northern Ireland models have been used to estimate the potential increase in flood risk
arising from climate change. The climate change sensitivity of the fluvial and coastal
flood risk was assessed by calculating the values of the annualised key flood risk
indicators using the predicted flood outlines for the low, medium and high probability
24 of 25
events relevant to the year 2030. The data used in the models for the year 2030 is
consistent with the increased rainfall predictions published in UKCP09. The values of the
flood risk indicators calculated for the year 2030 is contrasted with the ‘present day’
values at the 1km grid and sub-plan area scales to identify the geographical areas that are
particularly sensitive to the potential future impacts of climate change.
The climate change sensitivity for pluvial risk was assessed in a similar manner, except
that the 2100yr (climate change) outlines were used and not the 2030 yr. The risk arising
from potential land-use changes to catchments and coastal areas, particularly in relation to
the construction of new development has also been considered in Northern Ireland.
Planning Policy Statement 15 on Planning and Flood Risk has the aim of preventing future
development that may be at risk of flooding or that may give increase the risk of flooding
elsewhere. The climate change flood maps used in the PFRA are considered by the
Planning Service in the preparation of regional development plans and lands within flood
plains will not, save in exceptional circumstances, be included in future development
zones.
The Gibraltar Climate Change Programme (2008) which is currently being revised states
that the predicted effects of climate change in the Western Mediterranean are expected to
include lower levels of rainfall and a change in the distribution and intensity of rainfall.
This means that rainfall storms may become heavier leading to an increase in flooding.
The extent of flooding in the areas currently at risk could potentially increase therefore
with higher intensity rainfall events. If rainfall intensities increase, future flooding in the
town areas could affect some transport routes and cause damage to ground floors of offices
and residential buildings. Flooding events could also be affected in the future from the
potential impacts of climate change such as changes in sea level. The Gibraltar Climate
Change Programme (2008) indicates that a predicted increase in sea level in the order of
0.48m by 2100 is a reasonable figure to be applied to Gibraltar based on best estimates of
between 0.28 and 0.58m above 1989 to 1999 sea levels. All replacement sea defences
have taken account of potential sea level rise from climate change impacts so that the
height of the all new and upgraded sea walls are greater than predicted future sea levels.
There is no mention of potential changes in land use or planning being considered in the
PFRA.
Number of identified Areas of Potential Significant Flood Risk
Table 6 Areas of Potential Significant Flood Risk (APSFR) and types of consequences
Source: WISE Flood aggregation report: “FD 7.1 Areas of Potential Significant Flood Risk”
Member
State
Source
Mechanism
Characteristics Number
of
APSFR
Number with reported consequences
Human
Health
Environment Cultural
Heritage
Economic
Activity
UK Fluvial, 97 152 47 76 261
25 of 25
Pluvial
UK Fluvial,
Pluvial, Sea
water
161 263 124 143 456
UK Pluvial Natural
exceedance
Medium onset
flood
18 18 7 8 16
UK Pluvial, Sea
water
5 7 2 4 13
More than one type of consequence can be reported for each aggregated consequence (e.g. economic activity) for
each flood event, and therefore the totals in the consequence cells may be greater than the total number of flood
events reported for each type of flood
International coordination
MS were required to report how international cooperation had been achieved when undertaking a
PFRA under Article 4; and also for APSFR under Article 5. Those applying Article 13.1.a are
expected to have coordinated cooperation in the identification of APSFR but not necessarily for
the PFRA.
The relevant articles are:
Article 4. 3. In the case of international river basin districts, or units of management referred to in
Article 3(2)(b) which are shared with other Member States, Member States shall ensure that
exchange of relevant information takes place between the competent authorities concerned. And;
Article 5.2. The identification under paragraph 1 of areas belonging to an international river basin
district, or to a unit of management referred to in Article 3(2)(b) shared with another Member
State, shall be coordinated between the Member States concerned.
Number of international UoMs in the UK: 2
Number of non-international UoMs in the UK: 14
Table 7 Mechanisms of international coordination for preparation of PFRAs and
APSFRs
Type of coordination Number of UoMs
PFRAs APSFRs
International coordination and working groups – responsible for advice, decision-making, coordination, progress of work and/or implementation
2 2
Informal arrangement (groups, discussions and exchange of information)
2